Drying heat recovery - Page 2 - Industrial purification heat recovery

how does air to air heat exchanger work in nmp heat recovery

An air-to-air heat exchanger in NMP heat recovery transfers thermal energy between a hot, NMP-laden exhaust air stream from an industrial process and a cooler incoming fresh air stream, improving energy efficiency in industries like battery manufacturing.

The hot exhaust air (e.g., 80–160°C) and cooler fresh air pass through separate channels or over a heat-conductive surface (e.g., plates, tubes, or a rotary wheel) without mixing. Heat transfers from the hot exhaust to the cooler fresh air via sensible heat transfer. Common types include plate heat exchangers, rotary heat exchangers, and heat pipe heat exchangers.

NMP-specific designs use corrosion-resistant materials like stainless steel or glass fiber-reinforced plastic to withstand NMP’s aggressive nature. Larger fin spacing or clean-in-place systems prevent fouling from dust or residues. Condensation is managed to avoid blockages or corrosion.

The hot exhaust air transfers heat to the fresh air, preheating it (e.g., from 20°C to 60–80°C) and reducing energy needs for subsequent processes. The cooled exhaust air (e.g., 30–50°C) is sent to an NMP recovery system (e.g., condensation or adsorption) to capture and recycle the solvent. Heat recovery efficiency is 60–95%, depending on the design.

This reduces energy consumption by 15–30%, lowers greenhouse gas emissions, and improves NMP recovery by cooling the exhaust air for easier solvent capture. Challenges like fouling are addressed with wider gaps, extractable elements, or cleaning systems, while robust sealing prevents cross-contamination.

In a battery manufacturing plant, a plate heat exchanger preheats fresh air from 20°C to 90°C using 120°C exhaust air, reducing oven energy demand by ~70%. The cooled exhaust air is processed to recover 95% of NMP.

how does air to air heat exchanger work in wood drying

An air-to-air heat exchanger in wood drying transfers heat between two air streams without mixing them, optimizing energy efficiency and controlling drying conditions. Here's how it works:

Purpose in Wood Drying: Wood drying (kiln drying) requires precise temperature and humidity control to remove moisture from wood without causing defects like cracking or warping. The heat exchanger recovers heat from exhaust air (leaving the kiln) and transfers it to incoming fresh air, reducing energy costs and maintaining consistent drying conditions.
Components:
- A heat exchanger unit, typically with a series of metal plates, tubes, or fins.
- Two separate air pathways: one for hot, humid exhaust air from the kiln and one for cooler, fresh incoming air.
- Fans or blowers to move air through the system.
Working Mechanism:
- Exhaust Air: Hot, moisture-laden air from the kiln (e.g., 50–80°C) passes through one side of the heat exchanger. This air carries heat energy from the drying process.
- Heat Transfer: The heat from the exhaust air is conducted through the exchanger’s thin metal walls to the cooler incoming fresh air (e.g., 20–30°C) on the other side. The metal ensures efficient heat transfer without mixing the two air streams.
- Fresh Air Heating: The incoming air absorbs the heat, raising its temperature before it enters the kiln. This preheated air reduces the energy needed to heat the kiln to the desired drying temperature.
- Moisture Separation: The exhaust air, now cooler, may condense some of its moisture, which can be drained away, helping to control humidity in the kiln.
Types of Heat Exchangers:
- Plate Heat Exchangers: Use flat plates to separate air streams, offering high efficiency.
- Tube Heat Exchangers: Use tubes for air flow, durable for high-temperature applications.
- Heat Pipe Exchangers: Use sealed pipes with a working fluid to transfer heat, effective for large kilns.
Benefits in Wood Drying:
- Energy Efficiency: Recovers 50–80% of heat from exhaust air, lowering fuel or electricity costs.
- Consistent Drying: Preheated air maintains stable kiln temperatures, improving wood quality.
- Environmental Impact: Reduces energy consumption and emissions.
Challenges:
- Maintenance: Dust or resin from wood can accumulate on exchanger surfaces, requiring regular cleaning.
- Initial Cost: Installation can be expensive, though offset by long-term energy savings.
- Humidity Control: The system must balance heat recovery with proper moisture removal to avoid overly humid conditions.

In summary, an air-to-air heat exchanger in wood drying captures heat from exhaust air to preheat incoming air, improving energy efficiency and maintaining optimal drying conditions. It’s a critical component in modern kiln systems for sustainable, high-quality wood processing.

how does a heat exchanger work in a boiler

A heat exchanger in a boiler transfers heat from the combustion gases to the water circulating in the system. Here's how it works step by step:

Combustion occurs: The boiler burns a fuel source (like natural gas, oil, or electricity), creating hot combustion gases.
Heat transfer to the heat exchanger: These hot gases flow through a heat exchanger—typically a coiled or finned metal tube or series of plates made of steel, copper, or aluminum.
Water circulation: Cold water from the central heating system is pumped through the heat exchanger.
Heat absorption: As the hot gases pass over the surfaces of the heat exchanger, heat is conducted through the metal into the water inside.
Hot water delivery: The now-heated water is circulated through radiators or to hot water taps, depending on the boiler type (combi or system boiler).
Gas expulsion: The cooled combustion gases are vented out through a flue.

In condensing boilers, there's an extra stage:

After the initial heat transfer, the remaining heat in the exhaust gases is used to preheat incoming cold water, extracting even more energy and improving efficiency. This process often creates condensate (water), which is drained from the boiler.

Heat recovery device for whitening and defogging exhaust gas from paper mill drying

The exhaust gas generated by paper mills during the production process has the characteristics of high temperature, high humidity, and foul odor. If directly discharged, it not only pollutes the environment but also wastes a large amount of heat energy. To solve this problem, our company has developed a whitening and defogging heat recovery device for drying waste gas in paper mills.

Heat recovery device for whitening and defogging exhaust gas from paper mill drying
working principle:
Heat exchange principle: Using the principle of plate heat exchangers, heat is exchanged through a series of parallel metal plates. High temperature exhaust gas flows through one side of the plate, while fresh air flows through the other side, transferring heat through the plate wall to achieve waste heat recovery.
Cooling and heating process: Firstly, the high-temperature exhaust gas is cooled to a temperature close to the ambient temperature, and then heated by a reheater to make the exhaust gas temperature higher than the ambient temperature, thereby eliminating the phenomenon of white mist.
Technical advantages:
Efficient and energy-saving: By recovering waste heat from exhaust gas, energy consumption and operating costs are significantly reduced.
Environmental protection and emission reduction: effectively removing moisture and odorous components from exhaust gas, reducing pollution to the environment.
Compact structure: small size, light weight, easy installation, and occupies less space.
Application scenarios:
Paper industry: Recovering heat during the paper drying process to preheat the air entering the dryer, improve drying efficiency, and reduce fuel consumption.
Food processing industry: Recycling waste heat from the drying process of grains, vegetables, fruits, etc., to preheat fresh air and improve drying efficiency.
Chemical industry: Recycling high-temperature waste gas from the drying process of chemical products for heating other process gases or air.
Textile industry: used for the recovery of waste heat during the drying process of textiles, improving drying efficiency and energy-saving effects.

Heat pump drying heat recovery energy saving system

With the further development of China's economy, the use of green energy will be more and more extensive. Heat pump dehumidification dryers with plate type obvious heat recovery function have developed rapidly in recent years and have been widely used in the Yangtze River basin, southwest China and South China.

The unit using the inverse cano principle at the same time, combined with efficient heat recovery technology, in the whole drying dehumidifying process, through the duct the wet air within the chamber connected to the host using the sensible heat plate heat collector recovery of the sensible heat and latent heat of hot and humid air, thermal recycling, greatly improve the performance of the host, improve the drying speed and material quality. The waste heat can not only improve the performance of the unit, but also reduce the thermal pollution to the environment and alleviate the urban heat island effect.

The heat pump drying heat recovery system is not only used in the mud drying system, but also widely used in many other drying industries. It has the characteristics of good drying quality and high degree of automation, and is the best choice product for energy saving, green and environmental protection in the modern drying industry.

Heat pump dryers with and without heat recovery working principle

When the heat pump dryer dries the air, the air forms a closed cycle between the drying chamber and the equipment. The evaporator's heat absorption function is used to cool and dehumidify the hot and humid air, and the condenser's heat release function is used to heat the dry cold air, so as to achieve the effect of cycle dehumidification and drying.

The main difference between heat recovery function and heat pump dryers without heat recovery function lies in the different air circulation modes. The former is equipped with plate type sensible heat exchanger, which plays the function of pre-cooling and preheating in the air circulation process, reducing the load of compressor operation and achieving the purpose of energy saving.

Heat pump drying heat recovery energy saving system(图1)

Heat pump drying system operation mode

Heat pump drying heat recovery energy saving system(图2)

Energy saving analysis of heat recovery

Taking a heat pump dryer as an example, the air temperature of drying is designed to be 65℃, the relative humidity is 30%, the circulating air temperature is 65℃, the temperature before passing through the evaporator is 65℃, and the temperature after evaporation cooling is 35℃. The condenser needs to heat the air of 35℃ to 65℃ before it can be used.

After matching with BXB500-400-3.5 heat exchanger, 35℃ return air absorbs heat from exhaust air after passing through plate heat exchanger, and the temperature rises to 46.6℃. The condenser only needs to heat the air from 46.6℃ to 65℃ to meet the use requirements, greatly reducing the load of evaporator and condenser, thus reducing the power of the whole machine, achieving the purpose of energy saving.

Energy saving analysis of heat recovery

Heat pump drying heat recovery energy saving system(图3)

Selection and economic calculation

We are very glad to show you the calculation and selection software of plate heat exchanger jointly developed by us and Tsinghua University. If you need, please contact us!

Design of Drying, Dehumidification and Heat Recovery System

With the rapid development of manufacturing industry, many products require drying and dehumidification treatment during the production process. These processes not only require efficient moisture removal, but also require maintaining the characteristics and quality of the material. Traditional drying and dehumidification methods often consume high energy and may have adverse effects on the environment, such as emitting greenhouse gases and other pollutants.

By adopting efficient heat recovery technology, waste heat can be maximally recovered and reused to reduce energy consumption. Heat recovery technology has been widely applied in multiple industries to improve energy efficiency and reduce operating costs. But in the field of drying and dehumidification, the potential of this technology has not been fully tapped. We customize and develop a heat recovery system that suits your specific production needs and on-site conditions. We carefully design the system layout for you to ensure minimal loss of thermal energy during conversion and transmission. Welcome to inquire via email.

Ventilation heat exchanger for vegetable low-temperature processing area and supermarket sorting area

In the low-temperature vegetable processing area, the main function of the ventilation heat exchanger is to ensure that the temperature of the processing environment is suitable to maintain the freshness and quality of the vegetables. Ventilation heat exchangers use efficient heat exchange technology to dissipate indoor heat while introducing external cold air or cooled air for effective temperature control.
In addition, the ventilation heat exchanger in the low-temperature vegetable processing area also needs to consider humidity control, as excessive humidity may cause vegetable rot. Therefore, some ventilation heat exchangers are also equipped with humidity regulation functions to ensure that the humidity in the processing environment remains within an appropriate range.
The sorting area of a supermarket or shopping mall is responsible for sorting, packaging, and delivering goods. The main function of the ventilation heat exchanger in this area is to provide fresh air and remove indoor turbid air and excess heat.
The ventilation heat exchanger in the sorting area of supermarkets usually has a large air volume and efficient heat exchange performance to meet the needs of large spaces and high pedestrian flow. At the same time, they also need to have the characteristics of easy maintenance and cleaning to ensure long-term stable operation.
Whether it is a low-temperature vegetable processing area or a supermarket sorting area, ventilation heat exchangers are indispensable and important equipment. They provide a comfortable and healthy working environment for these areas through efficient air conditioning and temperature control, which helps improve production efficiency and product quality.
Our cross countercurrent plate heat exchanger is made of high-quality hydrophilic aluminum foil, epoxy resin aluminum foil, stainless steel, polycarbonate and other materials. The air flows partially in cross flow and partially in relative flow to avoid the transmission of odors and moisture. Applied to energy recovery in civil and commercial ventilation systems, as well as industrial ventilation systems. Fast heat conduction, no secondary pollution, good heat transfer effect.

Vegetable, tea, bean drying room, dehumidification and moisture removal air heat exchanger

Efficient dehumidification and dehumidification systems are required during the drying process of agricultural products such as vegetables, tea, and beans to ensure the quality and efficiency of the drying process. The gas heat exchanger plays a crucial role in this process. The following is a detailed introduction to the dehumidification and dehumidification system of vegetable, tea, and bean drying rooms.

Dehumidification process:
The humid and hot air in the drying room is drawn out by the exhaust fan and exchanges heat with the incoming dry air when passing through the air air heat exchanger.
After passing through the heat exchanger, the temperature of the discharged humid and hot air decreases, and the water vapor condenses into liquid water and is discharged.
The incoming dry air is preheated by a heat exchanger and enters the drying room, improving the drying efficiency.

Application scenarios
Vegetable drying: such as chili peppers, carrots, cabbage, etc., by controlling temperature and humidity, the color and nutrition of the dried vegetables are not destroyed.
Tea drying: For green tea, black tea, oolong tea, etc., the aroma and quality of the tea are maintained through appropriate temperature and humidity control.
Legumes drying: such as soybeans, mung beans, red beans, etc., are dried evenly with hot air to ensure the dryness and storage quality of the beans.

The application of gas air heat exchangers in vegetable, tea, and bean drying rooms has improved the energy efficiency and product quality of the drying process through efficient dehumidification and dehumidification functions. Reasonable design and use can significantly reduce energy consumption and operating costs, while being environmentally friendly, making it an indispensable part of modern drying technology.

Drying waste heat recovery

The heat pump drying heat recovery system can be applied to the drying of food, medicinal materials, tobacco, wood, and sludge. It has the characteristics of good drying quality and high degree of automation, and is the best and preferred product for energy-saving, green, and environmental protection in the modern drying industry.

The unit utilizes the reverse Carnot principle and efficient heat recovery technology. Throughout the entire drying and dehumidification process, the humid air in the drying room is connected to the main unit through a return air duct. The sensible and latent heat of the humid air is recovered using a sensible heat plate heat recovery device for heat recovery and reuse, greatly improving the performance of the main unit, drying speed, and material quality.

Recovery and utilization of waste heat from kiln drying: stainless steel welded plate air to air heat exchanger

Recovery and utilization of waste heat from kiln drying

Kiln drying waste heat recovery and utilization refers to the recovery and utilization of waste heat from the exhaust gas emitted by the kiln for drying materials, thereby improving energy utilization efficiency and reducing production costs.
Technical principle of waste heat recovery and utilization in kiln drying
The technical principle of waste heat recovery and utilization in kiln drying is to use a heat exchanger to transfer the heat from the kiln exhaust gas to fresh air, thereby heating the fresh air. The heated fresh air is used to dry materials, which can improve drying efficiency and reduce energy consumption.
Application of Waste Heat Recovery and Utilization in Kiln Drying
The technology of waste heat recovery and utilization in kiln drying can be applied to various kiln drying systems, including:
Brick and tile kiln drying
Ceramic kiln drying
Drying of building materials kilns
Chemical kiln drying
Food drying
Drying of agricultural and sideline products
The advantages of recycling and utilizing waste heat from kiln drying
The recovery and utilization of waste heat from kiln drying have the following advantages:
Energy saving: It can effectively utilize the waste heat in the kiln exhaust gas, reduce energy consumption, and lower production costs.
Environmental protection: It can reduce exhaust emissions and reduce environmental pollution.
Improving drying efficiency: can improve drying efficiency, shorten drying time, and improve product quality.
Common methods for recovering and utilizing waste heat from kiln drying
The common methods for recovering and utilizing waste heat from kiln drying include:
Waste heat recovery from flue gas: Using a heat exchanger to transfer the heat in the flue gas to fresh air for drying materials.
Kiln body waste heat recovery: Using the waste heat of the kiln body to heat fresh air for drying materials.
Waste heat drying kiln: Directly use kiln exhaust gas to dry materials.
Notes on the recovery and utilization of waste heat from kiln drying
When recovering and utilizing waste heat from kiln drying, the following precautions should be taken:
Choose a suitable waste heat recovery device: The appropriate waste heat recovery device should be selected based on factors such as kiln type, drying materials, and residual heat.
Ensure heat exchange efficiency: The heat exchange device should be regularly inspected and maintained to ensure heat exchange efficiency.
Prevent corrosion: Measures should be taken to prevent corrosion of the waste heat recovery device.
With the continuous improvement of energy conservation and emission reduction requirements, the technology of waste heat recovery and utilization in kiln drying will be increasingly widely applied.

Industrial purification heat recovery

Category Archive Drying heat recovery